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Is this enough information to determine an adoptee's father?

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  • Is this enough information to determine an adoptee's father?

    I’m helping an adoptee to learn who his birth father was. (We already know about his birth mother.) He has several DNA matched first cousins from his paternal line (most are on Ancestry), and with their help, we have been able to narrow down the possible fathers to three brothers – Tony, Bill, or Hank (not their real names). All were in the military during WWII, when the adoptee was conceived, and all of them are now deceased.

    Tony had no known children, so he has no descendants to test.

    Bill had two known children (both now deceased); he has one living granddaughter who took a DNA test (results transferred to FTDNA for comparison).

    Hank had one known child (a son) who is considering whether or not to have a DNA test done.

    Based on their known whereabouts during the war, the most likely father is Bill. However, the other two brothers cannot be completely ruled out.

    Bill’s granddaughter and the adoptee share 783 cM; the longest block is 97.

    Using the DNA Painter – Shared cM Project calculator (with relationship probabilities), the only options that fit are either half-uncle/half-niece or first cousins once removed (1C1R).

    According to the calculator, there is a 91.14 percent probability that the adoptee and Bill’s granddaughter are half-uncle/half-niece; and there is an 8.86 percent probability that they are 1C1R.

    Under these circumstances, is there any way we can know for sure if the adoptee is, in fact, Bill’s son? Would the chromosome browser in FTDNA help to determine this, and if so, what should I look for while I’m viewing those results? Would it help to know that another confirmed 1C and 1C1R are FTDNA matches as well?

    Thank you for any help you can give us to bring closure for this adoptee and his family.